Recovery of caloric function in experimental perilymph fistula

Usher syndrome and cochlear implantation

OBJECTIVE

To evaluate the symptoms leading to diagnosis and the quality of rehabilitation after cochlear implantation in Usher syndrome.

STUDY DESIGN

Retrospective cohort study.

SETTING

ENT department of a tertiary referral hospital.

PATIENTS

Among 210 patients given an implantation in the Ear, Nose, and Throat department, 185 were congenitally deaf and 13 had Usher syndrome (7.0%). Five had a family history of Usher, and eight were sporadic cases. Eleven cases were Usher type I, one was Usher type III, and one was not classified. The age at implantation ranged from 18 months to 44 years (mean, 6 years 1 month). The mean follow-up was 52 months (range, 9 months to 9 years).

MAIN OUTCOME MEASURES

All patients had audiophonological and clinical examination, computed tomography scan of the temporal bones, ophthalmologic examination with fundoscopy, and an electroretinogram. Cerebral magnetic resonance imaging and vestibular examination were performed in 9 of 13 and 10 of 13 cases, respectively. Logopedic outcome measured preimplant and postimplant closed- and open-set word recognition and oral expression at follow-up.

RESULTS

The most frequent initial sign of Usher syndrome was delayed walking, with a mean age of 20 months. Among the 172 other congenitally deaf children with implants, when deafness was not associated with other neurologic disorders, the mean age at walking was 14 months (p < 0.001). The fundoscopy was always abnormal after the age of 5 years, and the electroretinogram was abnormal in all cases. Vestibular function was abnormal in all but one case (nonclassified). The computed tomography scan and the magnetic resonance imaging were always normal. Logopedic results with cochlear implants showed good perception skills in all but one case. The best perceptive results were obtained in children implanted before the age of 9 years. Oral language had significantly progressed in 9 of 13 at follow-up. There was no relation between the visual acuity and the logopedic results.

CONCLUSION

The earliest clinical sign associated with deafness evoking Usher syndrome is late walking. The electroretinogram is the only reliable examination to enable the diagnosis. When severe profound deafness is associated with late walking, the electroretinogram should be systematically proposed. Logopedic results are linked to precocity of implantation, and early Usher's diagnosis contributes to optimize speech therapy.

Suppression of post-caloric nystagmus in experimental perilymph fistula

Albino guinea pigs (n = 28) were used to establish an animal model of the perilymph fistula (PLF) by suctioning 2-4 microliters of perilymph via the left round window membrane. At times varying from 1-3 weeks post-operatively, 9 animals had no caloric response, 5 had a weak caloric response and none had post-caloric nystagmus (PCN). The remaining 14 animals had caloric irregularity in lesioned ears; 12 of these (87%) also did not have PCN. Morphological study of the latter revealed an intact contour of the membranous labyrinth in the lateral semicircular duct and partial collapse of the utricular wall, a condition called the "floating labyrinth". We therefore believe that effective suppression of PCN in the experimental PLF is due to failure in short-term adaptation, caused by lesions in the peripheral vestibular organs, such as the floating labyrinth.